The catalytic domain of a protein kinase is? (Select the best answer) A. transfe

Question

The catalytic domain of a protein kinase is? (Select the best answer)

A. transfers a phosphate group to the relevant amino acid of the target protein.
B. binds to Ca2+ ions.
C. transfers a carboxyl group to the relevant amino acid of the target protein.  
D. transfers ATP to the relevant amino acid of the target protein.

Which role does calmodulin play in the intracellular cascade triggered by Ca2+? (Select the best answer)

A. It serves as a Ca2+ sensor when neurotransmitter is released.
B. It binds to its downstream targets when activated by Ca2+.
C. It serves as a Ca2+ buffer.
D. It modulates the strength of Ca2+ binding to its downstream targets

Cell X fires an action potential and releases GABA onto Cell Y. Assuming only GABAA receptors are present on the postsynaptic membrane, which is at rest at –55mV, which ion is responsible for the changes that would be observed? (Select the best answer)

A. Sodium  
B. Chloride  
C. Potassium
D. Calcium

Explanation / Answer

1. Option A is the correct answer. Protein kinase is a group of enzymes which transfer a phosphate group to the relevent amino acid of the target protein. Protein kinase is generally activated when level of cGMP (cyclic guanosine monophosphate) increases within a cell.

2. Option B is correct. Clamodulin (calcium modulated protein)is a multifunctional intermediate calcium-binding messenger protein which is activated upon binding of calcium ion leading to confirmational changes in clamodulin allowing calcium complex (Ca2+-CaM) to bind to its targets, eliciting certain responses.

3. Option B is the correct answer. There are two types of GABA receptors GABAA and GABAB. These receptors activates upon binding with its ligand gamma amino butyric acid (neurotransmitter). GABAA  opens chloride ion channel upon activation leading to hyperpolarization. This causes an inhibitory effect on neurotransmission by diminishing the chance of a successful action potential occurring. GABAB receptors are G-protein coupled receptors which are linked to potassium channel via G-protein. GABAB causes a change in potassium ion concentration leading to hyperpolarization.

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